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homography.py
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homography.py
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import os
import cv2
import numpy as np
# handle click on image for point definition
def click_event(event, x, y, flags, params):
if event == cv2.EVENT_LBUTTONDOWN:
# memorize coordinates
x1.append(x)
y1.append(y)
# overlay clicked images
font = cv2.FONT_HERSHEY_SIMPLEX
cv2.putText(img_shown, str(x) + ',' +
str(y), (x, y), font,
1, (0, 255, 0), 2)
cv2.imshow('Select 4 points and press ENTER', img_shown)
if __name__ == "__main__":
# reading the image
img_src_name = 'Image.jpeg'
img_src = cv2.imread(img_src_name, 1)
img_shown = np.copy(img_src)
width = img_src.shape[1]
height = img_src.shape[0]
# display image
cv2.imshow('Select 4 points and press ENTER', img_shown)
x1 = []
y1 = []
pts_final = np.array([[0, 0], [width, 0], [width, height], [0, height]])
cv2.setMouseCallback('Select 4 points and press ENTER', click_event)
# wait for a key to be pressed to exit
cv2.waitKey(0)
cv2.destroyAllWindows()
# homography computation
n = 4
A = np.zeros((n * 3, 9))
x2 = pts_final[:, 0]
y2 = pts_final[:, 1]
for i in range(n):
tmp = np.array([[x1[i], y1[i], 1, 0, 0, 0, -x2[i] * x1[i], -x2[i] * y1[i], -x2[i]],
[0, 0, 0, x1[i], y1[i], 1, -y2[i] * x1[i], -y2[i] * y1[i], -y2[i]]])
A = np.concatenate((A, tmp), axis=0)
u, s, v = np.linalg.svd(A, full_matrices=False)
H = v[-1].reshape(3, 3)
# apply homography
img_dst = cv2.warpPerspective(img_src, H, (width, height))
# write and open destination image
img_dst_name = 'res-' + img_src_name
cv2.imwrite('res-' + img_src_name, img_dst)
os.system('open /System/Applications/Preview.app ' + img_dst_name)